Dehydration is a significant problem for the elderly population since the body composition of water changes during aging towards a drier state. Elderly subjects have a tendency to drink too little during daytime. This fact in combination with slight hypoaldosteronism, a reduced sensation of thirst, an impaired ability to concentrate urine and, in many cases, forgetfulness to drink can lead to significant dehydration and a cumbersome situation for both patients and caregivers. The consequences of dehydration are several and sometimes severe; conditions such as vertigo and imbalance leading to falls, urinary- and respiratory infections with or without septicaemia, delirium, renal failure and increased risk for medication toxicity. Elderly with many co-morbidities are at an increased risk for repeated hospitalizations and dehydration has been associated with an increased mortality among hospitalized older adults